}

// NewReader creates a new trace reader.
func NewReader(r io.Reader) (*Reader, error) {
	br := bufio.NewReader(r)
	v, err := version.ReadHeader(br)
	if err != nil {
		return nil, err
	}
	switch v {
	case version.Go111, version.Go119, version.Go121:
		tr, err := oldtrace.Parse(br, v)
		if err != nil {
			return nil, err
		}
		return &Reader{
			go121Events: convertOldFormat(tr),
		}, nil

	errTooMuch   = errors.New("gif: too much image data")
	errBadPixel  = errors.New("gif: invalid pixel value")
)

// If the io.Reader does not also have ReadByte, then decode will introduce its own buffering.
type reader interface {
	io.Reader
	io.ByteReader
}

// Masks etc.
const (
	// Fields.
	fColorTable         = 1 << 7
	fInterlace          = 1 << 6
	fColorTableBitsMask = 7

	"strconv"
	"strings"
	"time"
)

// Reader provides sequential access to the contents of a tar archive.
// Reader.Next advances to the next file in the archive (including the first),
// and then Reader can be treated as an io.Reader to access the file's data.
type Reader struct {
	r    io.Reader
	pad  int64      // Amount of padding (ignored) after current file entry
	curr fileReader // Reader for current file entry

// the size of responses.
func NewReader(r *bufio.Reader) *Reader {
	return &Reader{R: r}
}

// ReadLine reads a single line from r,
// eliding the final \n or \r\n from the returned string.
func (r *Reader) ReadLine() (string, error) {
	line, err := r.readLineSlice(-1)
	return string(line), err
}

// ReadLineBytes is like [Reader.ReadLine] but returns a []byte instead of a string.

}

// A Reader reads records from a CSV-encoded file.
//
// As returned by [NewReader], a Reader expects input conforming to RFC 4180.
// The exported fields can be changed to customize the details before the
// first call to [Reader.Read] or [Reader.ReadAll].
//
// The Reader converts all \r\n sequences in its input to plain \n,

// [CanonicalHeaderKey].
func (h Header) Del(key string) {
	textproto.MIMEHeader(h).Del(key)
}

// Write writes a header in wire format.
func (h Header) Write(w io.Writer) error {
	return h.write(w, nil)
}

func (h Header) write(w io.Writer, trace *httptrace.ClientTrace) error {
	return h.writeSubset(w, nil, trace)
}

// Clone returns a copy of h or nil if h is nil.
func (h Header) Clone() Header {
	if h == nil {

	"fmt"
	"io"

	"internal/trace/event"
	"internal/trace/version"
)

// Reader parses trace bytes with only very basic validation
// into an event stream.
type Reader struct {
	r     *bufio.Reader
	v     version.Version
	specs []event.Spec
}

// NewReader creates a new reader for the trace wire format.
func NewReader(r io.Reader) (*Reader, error) {
	br := bufio.NewReader(r)
	v, err := version.ReadHeader(br)

// AST reader

// reader accumulates documentation for a single package.
// It modifies the AST: Comments (declaration documentation)
// that have been collected by the reader are set to nil
// in the respective AST nodes so that they are not printed
// twice (once when printing the documentation and once when
// printing the corresponding AST node).
type reader struct {
	mode Mode

# Header-Parameter

So wie `Query`-, `Path`-, und `Cookie`-Parameter können Sie auch <abbr title='Header – Kopfzeilen, Header, Header-Felder: Schlüssel-Wert-Metadaten, die vom Client beim Request, und vom Server bei der Response gesendet werden'>Header</abbr>-Parameter definieren.

## `Header` importieren

Importieren Sie zuerst `Header`:

=== "Python 3.10+"

    ```Python hl_lines="3"
    {!> ../../../docs_src/header_params/tutorial001_an_py310.py!}

    {!> ../../../docs_src/header_params/tutorial001.py!}
    ```

!!! note "技术细节"

    `Header` 是 `Path`、`Query`、`Cookie` 的**兄弟类**，都继承自共用的 `Param` 类。

    注意，从 `fastapi` 导入的 `Query`、`Path`、`Header` 等对象，实际上是返回特殊类的函数。

!!! info "说明"

    必须使用 `Header` 声明 header 参数，否则该参数会被解释为查询参数。

## 自动转换

`Header` 比 `Path`、`Query` 和 `Cookie` 提供了更多功能。

大部分标准请求头用**连字符**分隔，即**减号**（`-`）。